I got a chance to look at the videos and it really does seem like you're the only one even doing anything in there given that the framerate with everyone fighting koldrak is usually low and you were constantly around 40+ fps.
I'm not exactly sure if you're able to reenter a different koldrak after exiting an incomplete one. Since you do koldraks from alts given what you said already, then if you see the dragon's health higher than 75-80% after the first tail knockback, I'd advise to leave the dragon and go on another alt if you can since the average health range of the dragon on the first pushback is usually around 35-65% hp.
That's all I can really tell you, but it does suck. I had to leave a koldrak on my 2.3k bd alt as well a few days ago and I decided to do dragon on another alt as a result since I realized the damage was either too low or too many people afk'ing.